Subsurface fertilizer banding by using a conventional knife applicator is one of the most common methods for nitrogen (N) fertilization of corn in the North Central Region of the USA. A knife is pulled through the soil to open a furrow into which a fertilizer can be injected. Anhydrous ammonia (NH.sub.3) is the most widely used N-source in this type of application, but solutions such as urea ammonium nitrate (often designed UAN) are also used. Knifing incorporates the N fertilizer so that volatilization losses of NH.sub.3 can be limited. However, N fertilizer losses by nitrate-nitrogen (NO.sub.3 --N) leaching from the root zone are as troubling as losses to volatilization, because of the environmental and health risks associated with NO.sub.3 --N contamination of and surface water resources receiving subsurface drainage water resources. High concentrations of NO.sub.3 --N in rural drinking water wells suggest that conventional fertilizer application practices should be evaluated and perhaps adapted to prevent agricultural N from impacting water quality.
Conventional knifing techniques leave a porous slit above the injected fertilizer. This knife slit creates a soil zone more favorable to water movement than the surrounding soils. Thus, two soil zones are created: 1) undisturbed soil with small N fertilizer concentration; and 2) loose, porous, and disturbed soil with large N fertilizer concentration. The physical properties of these two zones are very different, and the normal practice is to leave them in this state. Additional management of the soil is necessary to reduce water movement through the fertilizer band and the probability of N movement from the fertilized zone.
Conventional tillage after chemical application, which mixes the fertilized soil and reduces macropore continuity, delays chemical breakthrough deeper in the soil compared with no-till systems. The presence of numerous macropores allows rapid flow of water deep into the soil. If that rapidly moving water contacts NO.sub.3 --N fertilizer, then the chemical is moved rapidly as well. Studies of solute movement under ridge tillage management indicate that solutes are less susceptible to leaching if they are placed under the ridge peak instead of in the ridge valley. In these instances, chemicals are placed in positions where water is less likely to infiltrate, thus chemical movement and leaching are reduced. Finally, the presence of a compacted layer near the fertilized zone slows the flow of water and chemical leaching by altering the water flow path around the barrier.
However, equipment and a method for dealing with the foregoing problems do not exist in a single apparatus or method of applying the N fertilizer.
It is therefore a principal object of this invention to provide an apparatus and a method for simultaneously accomplishing the following:
1) remove the macropore flow pathways immediately below the fertilizer band; PA1 2) close the knife slit that forms during conventional application techniques; PA1 3) form a compacted soil layer above the fertilizer band to impede the flow of infiltrating surface water and divert the water away from the fertilizer band; and PA1 4) form a dome over the fertilizer band to direct any surface runoff away from the band so that the water infiltrates the soil via a furrow away from the fertilizer band.
These and other objects will be apparent to those skilled in the art.